My stock answer is that you don't need a mechanic, you need an electrician. These days I might need to update it and say you need a computer programmer.

My one and only beef about electronic shifting is that it's not amenable to problem solving by observation and analysis. Something totally invisible, like a sloppy internal connection, a program glitch, or whatever can be the issue, but there's no way to tell.

My SOP for stuff like this, on all electronics, is to power down, remove the battery, let it rest for long enough for any residual charges to drain or equalize. Then power back up and hope for the best. Sometimes I'm lucky, and sometimes I restrain my impulses to chuck it out a window.